<!-- 
    
 -->
<html>

<head>
    <title>Canvas tutorial</title>
    <script type="text/javascript">
        function draw() {
            var ctx = document.getElementById('canvas').getContext('2d');
            for (var i = 0; i < 6; i++) {
                for (var j = 0; j < 6; j++) {
                    ctx.strokeStyle = 'rgb(0,' + Math.floor(255 - 42.5 * i) + ',' +
                        Math.floor(255 - 42.5 * j) + ')';
                    ctx.beginPath();
                    ctx.arc(12.5 + j * 25, 12.5 + i * 25, 10, 0, Math.PI * 2, true);
                    ctx.stroke();
                }
            }
        }
    </script>
    <style type="text/css">
        canvas {
            border: 1px solid black;
        }
    </style>
</head>

<body onload="draw();">
    <canvas id="canvas" width="500" height="500"></canvas>
</body>

</html>